In a video distribution system or the like, an excess of bandwidth capacity sometimes occurs on a network that connects a video distribution server and terminals, due to an increase in access to a particular video content and the like. There is a known technique of reducing overall traffic volume by performing bandwidth reduction on part of traffic as a countermeasure against such an excess of bandwidth capacity.
For example, PTL 1 discloses a method of avoiding saturation of a network bandwidth when the bandwidth is to saturate. In the method described in PTL 1, a quantity of data of at least one victim stream is reduced using a compression technique or the like. PTL 1 illustrates, as one method of selecting a victim stream whose data are to be reduced, a method in which a stream that has the greatest quantity of data is selected.
Further, PTL 2 discloses a method of controlling network congestion. In the method disclosed in PTL 2, a packet of a malignant flow is tagged to indicate that the packet is precedentially discarded. A malignant flow is identified on the basis of feature information such as a duration and a communication volume of the flow.
Further, PTL 3 discloses an information intermediary device that controls congestion. In a method described in PTL 3, the information intermediary device controls an invalid flow that performs communication that exceeds a contracted bandwidth capacity. The information intermediary device selects, as an invalid flow, a flow that has the number of packets that exceeds a threshold value.